Figure 1: A Walrus shown in its native environment of the Arctic Ice. Source: http://images.pictureshunt.com/pics/w/walrus-8925.jpg
Habitat
Walruses are known to live in a large area, almost forming a circular region around the Arctic, sharing the same habitat as Polar bears, which are its natural predators and having similar living conditions with the Leopard seals. The three different subspecies each live in a different sector. The Atlantic Walrus lives in the Eastern Canadian Arctic and Greenland east to Novaya Zemlya. The Pacific Walrus lives in the Berling Sea and Adjacent Arctic Ocean, while the Laptev Walrus lives in the Laptev Sea north of Siberia (This sub-species is sometimes controversial and not accepted).
Walruses like to live in shallower regions of water in areas with ice floes, which are often near the coast of Arctic waterways. Ice floes are flat pieces of sea ice that can move around freely in the water, and can vary in size greatly from over 10 kilometres across to only around 100 meters. They migrate according to the seasons, and in winter the Walruses move south as the ice expands outwards to find better hunting grounds as old water freezes over. In summer, they retreat back to the north as the ice starts to melt and their living places are in danger. They can migrate as much as over 3000 kilometres in search of suitable grounds to settle in. They move out to the edge of these ice floes, as this is where the ice stops and the water starts, which is also the besting hunting ground for the Walruses to find food. While the female Walruses and young prefer to stay in ice floes all year round, male walruses may occasionally find coastal beaches or rocky islets to stay in temporarily during the summer. Once settled in, Walruses find food in the water at the surface of the ocean floor bottom. There, they can find mussels, snails, echinoderms and crabs, which make up their main diet. They need to hunt often, and require 6% of their body weight in terms of food each day, which is no small amount when taking the fact that Walruses can weigh up to 2000 kg, although most are only around 800-1800 kg. Their diet has also been known to include fish, seals or young whales if they happen to cross paths or are extremely hungry. Walruses dives lasts on average of 2 to 10 minutes each time up to depths of 80 meters, although they can remain under the water for up the 30 minutes before surfacing for air. As mentioned before they prefer to stay in areas with shallower waters because they cannot dive to ocean floor bottoms of deeper regions to find food.
The Arctic environment they live in is very cold, however Walruses prefer to stay in areas with a temperature of around -15º to +5ºC. There are always constant strong winds and the water is freezing as well, so the Walruses have adapted to the environment to survive. They spend around half to two-thirds of their life in the ice, outside of water, where they spend time to interact with other Walruses.
Figure 2: This picture shows the Arctic Circle and the distribution of Walruses around the area. Source: http://newsimg.bbc.co.uk/media/images/42703000/gif/_42703977_walrus_dis_416.gif
Figure 3: A diagram showing the Walruses’ adaptation which helps them survive. Source: http://desktopnature.com/1340-2/Walrus+Bull.jpg
Behavioral Adaption
Walruses are very dependent on each other for living because they migrate and live together in several thousand individuals in close proximity. By staying together in groups, they increase their chance of survival. Sticking together has the advantage of strength in numbers, which deter predators such as polar bears away from attacking them. Their young are also more protected in the center of the group, so that they won’t be eaten or killed as easily by other animals. In addition, being close together means that they can share their body heat to conserve energy in the freezing temperatures, and because both the males and females are together, they can mate more easily. The walruses that don’t stay in these groups will often be picked off by predators because they are easy prey by themselves, and because they don’t see another walrus of the opposite sex as often, will not be able to procreate as easily, sometimes dying because they can pass on their genes. These factors forced the Walruses to live together in packs for survival.
Walruses mate during January to February, and have a mating system in which the males must compete with each other to gain the exclusive rights to mate with herds of females. Their courtship behaviour involves singing and other noises via sharp clicking or whistles both in and out of water. This is used to attract the attention of the females and to make them be chosen for mating. However, often a fight is involved in which two male walruses will fight each other and tries to scare or injure the other away. They use their tusks as weapons and try to intimidate other males into submission. These behaviours are done so to ensure that the males with the best characteristics such as having better physical strength or agility will be able to mate more often, which in turn will mean that their genes gets passed on more often and become more common. The survival of the species is helped by this as the future generation will have a better chance of living longer, and Walruses will adapt and evolve through reproduction to better live in the environment.
Figure 4: A large group of Walruses resting together on the beach. Source: http://www.alaska-in-pictures.com/data/media/1/bristol-bay-walrus-group_6065.jpg
Structural Adaption
The Walruses have very large tusks which are found in both males and females, although they are more prominent and grow larger in males, sometimes growing longer than 100 cm, (60 cm in females). They can be compared to the tusks of the African Elephant. This is because it is used as both a decoration to impress the females, and to fight against other male walruses in an attempt to compete for mating rights with a female. The males with larger tusks often win the fight, and thus they get to mate and pass on their genes of larger tusks to the next generation, also it can be used as a weapon against the natural predators such as polar bears and killer whales, so the walruses with the more effective weapon will survive more often against them and live on to pass their genes. This is why now the males have slightly larger tusks than females in general.
Another adaption that the Walrus has undergone as a direct result of their larger tusks is that their skull must become stronger in order to be able to lift the heavy tusks around easily. Their facial bone structure has changed slightly over time to better fit the tusks, by rooting it into the skull more tightly, and at the back of their skull more muscles have developed for better mobility of the head with powerful muscles to pull the head downwards, which accounts for the extra weight of the tusks. This is because the walruses that develop larger tusks but then have a head structure that cannot lift them easily, will most likely die due to them being at a large disadvantage: they cannot look around as easily and see or run away from predators, and they will not be able to hunt as well because they can’t see their prey. This means that the walruses that do adapt to the tusks will have a higher chance to survive and pass on their genes, which is why now most walruses have a different facial bone structure and more muscles than before.
Figure 5: The head of a Walrus, showing the long tusks and large skull and muscles. Source: http://www.seaworld.org/animal-info/info-books/walrus/images/pic-head.jpg
Physiological Adaption
Walruses also have a special physiology to help them survive. Their skin is made up of many folds and wrinkles, and can be up to 10 cm at the thickest point in their necks. Underneath that is a thick layer of blubber, which is fat that can become up to 15 cm thick. This is used to not only to store energy in the form of fat, but also helps keep them warm, and in case they are not able to hunt for a while, so they can survive without food for a short period of time. Their skin blood vessels constrict while in the water, which further helps protect them from the cold temperatures of the arctic. This gives their skin an almost white colour when in the water, while out of the water they can appear in a pink colour if their temperature is hot. These characteristics in the skin helps Walruses survive as they will conserve more energy by keeping their body temperature warm, leaving the other energy for them to hunt and live. This adaption to the frigid environment helps them because otherwise they would suffer from the cold and can die of hyperthermia or other similar causes or not be able to hunt as effectively, having to use more energy to keep themselves warm. The environmental factor which leads to this adaption was that the walruses which had less fat would often die easily in the cold temperatures, leaving the ones who were well suited for living with better skins to pass on their genes.
Figure 6: Close up picture of the Walruses' wrinkled and thick skin. Source: http://www.arkive.org/media/47/475895AC-ABA2-4FD9-B77A-A2B2075AC254/Presentation.Large/photo.jpg
Reference
Encyclopedia of Life. (2010). Odobenus rosmarus (Linnaeus, 1758). Retrieved July 15, 2010, from http://www.eol.org/pages/328627
Future Animal Page: Odobenus Teres
Habitat
Walruses are known to live in a large area, almost forming a circular region around the Arctic, sharing the same habitat as Polar bears, which are its natural predators and having similar living conditions with the Leopard seals. The three different subspecies each live in a different sector. The Atlantic Walrus lives in the Eastern Canadian Arctic and Greenland east to Novaya Zemlya. The Pacific Walrus lives in the Berling Sea and Adjacent Arctic Ocean, while the Laptev Walrus lives in the Laptev Sea north of Siberia (This sub-species is sometimes controversial and not accepted).
Walruses like to live in shallower regions of water in areas with ice floes, which are often near the coast of Arctic waterways. Ice floes are flat pieces of sea ice that can move around freely in the water, and can vary in size greatly from over 10 kilometres across to only around 100 meters. They migrate according to the seasons, and in winter the Walruses move south as the ice expands outwards to find better hunting grounds as old water freezes over. In summer, they retreat back to the north as the ice starts to melt and their living places are in danger. They can migrate as much as over 3000 kilometres in search of suitable grounds to settle in. They move out to the edge of these ice floes, as this is where the ice stops and the water starts, which is also the besting hunting ground for the Walruses to find food. While the female Walruses and young prefer to stay in ice floes all year round, male walruses may occasionally find coastal beaches or rocky islets to stay in temporarily during the summer. Once settled in, Walruses find food in the water at the surface of the ocean floor bottom. There, they can find mussels, snails, echinoderms and crabs, which make up their main diet. They need to hunt often, and require 6% of their body weight in terms of food each day, which is no small amount when taking the fact that Walruses can weigh up to 2000 kg, although most are only around 800-1800 kg. Their diet has also been known to include fish, seals or young whales if they happen to cross paths or are extremely hungry. Walruses dives lasts on average of 2 to 10 minutes each time up to depths of 80 meters, although they can remain under the water for up the 30 minutes before surfacing for air. As mentioned before they prefer to stay in areas with shallower waters because they cannot dive to ocean floor bottoms of deeper regions to find food.
The Arctic environment they live in is very cold, however Walruses prefer to stay in areas with a temperature of around -15º to +5ºC. There are always constant strong winds and the water is freezing as well, so the Walruses have adapted to the environment to survive. They spend around half to two-thirds of their life in the ice, outside of water, where they spend time to interact with other Walruses.
Behavioral Adaption
Walruses are very dependent on each other for living because they migrate and live together in several thousand individuals in close proximity. By staying together in groups, they increase their chance of survival. Sticking together has the advantage of strength in numbers, which deter predators such as polar bears away from attacking them. Their young are also more protected in the center of the group, so that they won’t be eaten or killed as easily by other animals. In addition, being close together means that they can share their body heat to conserve energy in the freezing temperatures, and because both the males and females are together, they can mate more easily. The walruses that don’t stay in these groups will often be picked off by predators because they are easy prey by themselves, and because they don’t see another walrus of the opposite sex as often, will not be able to procreate as easily, sometimes dying because they can pass on their genes. These factors forced the Walruses to live together in packs for survival.
Walruses mate during January to February, and have a mating system in which the males must compete with each other to gain the exclusive rights to mate with herds of females. Their courtship behaviour involves singing and other noises via sharp clicking or whistles both in and out of water. This is used to attract the attention of the females and to make them be chosen for mating. However, often a fight is involved in which two male walruses will fight each other and tries to scare or injure the other away. They use their tusks as weapons and try to intimidate other males into submission. These behaviours are done so to ensure that the males with the best characteristics such as having better physical strength or agility will be able to mate more often, which in turn will mean that their genes gets passed on more often and become more common. The survival of the species is helped by this as the future generation will have a better chance of living longer, and Walruses will adapt and evolve through reproduction to better live in the environment.
Structural Adaption
The Walruses have very large tusks which are found in both males and females, although they are more prominent and grow larger in males, sometimes growing longer than 100 cm, (60 cm in females). They can be compared to the tusks of the African Elephant. This is because it is used as both a decoration to impress the females, and to fight against other male walruses in an attempt to compete for mating rights with a female. The males with larger tusks often win the fight, and thus they get to mate and pass on their genes of larger tusks to the next generation, also it can be used as a weapon against the natural predators such as polar bears and killer whales, so the walruses with the more effective weapon will survive more often against them and live on to pass their genes. This is why now the males have slightly larger tusks than females in general.
Another adaption that the Walrus has undergone as a direct result of their larger tusks is that their skull must become stronger in order to be able to lift the heavy tusks around easily. Their facial bone structure has changed slightly over time to better fit the tusks, by rooting it into the skull more tightly, and at the back of their skull more muscles have developed for better mobility of the head with powerful muscles to pull the head downwards, which accounts for the extra weight of the tusks. This is because the walruses that develop larger tusks but then have a head structure that cannot lift them easily, will most likely die due to them being at a large disadvantage: they cannot look around as easily and see or run away from predators, and they will not be able to hunt as well because they can’t see their prey. This means that the walruses that do adapt to the tusks will have a higher chance to survive and pass on their genes, which is why now most walruses have a different facial bone structure and more muscles than before.
Physiological Adaption
Walruses also have a special physiology to help them survive. Their skin is made up of many folds and wrinkles, and can be up to 10 cm at the thickest point in their necks. Underneath that is a thick layer of blubber, which is fat that can become up to 15 cm thick. This is used to not only to store energy in the form of fat, but also helps keep them warm, and in case they are not able to hunt for a while, so they can survive without food for a short period of time. Their skin blood vessels constrict while in the water, which further helps protect them from the cold temperatures of the arctic. This gives their skin an almost white colour when in the water, while out of the water they can appear in a pink colour if their temperature is hot. These characteristics in the skin helps Walruses survive as they will conserve more energy by keeping their body temperature warm, leaving the other energy for them to hunt and live. This adaption to the frigid environment helps them because otherwise they would suffer from the cold and can die of hyperthermia or other similar causes or not be able to hunt as effectively, having to use more energy to keep themselves warm. The environmental factor which leads to this adaption was that the walruses which had less fat would often die easily in the cold temperatures, leaving the ones who were well suited for living with better skins to pass on their genes.
Reference
Encyclopedia of Life. (2010). Odobenus rosmarus (Linnaeus, 1758). Retrieved July 15, 2010, from http://www.eol.org/pages/328627
Wikipedia. (2010). Walrus. Retrieved July 14, 2010, from http://en.wikipedia.org/wiki/Walrus
Sea World. (2010). Walrus. Retrieved July 15, 2010, from http://www.seaworld.org/animal-info/info-books/walrus/habitat-%26-distribution.htm
Walrus World. (2010). Walrus Facts and Information. Retrieved July 16, 2010, from http://www.walrus-world.com/